JP2002341189A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module whose productivity is high. SOLUTION: The optical module is provided with at least a semiconductor laser 6, a first sphere lens 1 which collimates emitted light from the semiconductor laser 6, and a second sphere lens 2 for optically connecting the collimated light to an optical fiber 14, and a matching operation of the semiconductor laser 6, the optical axis of the first lens 1, and the optical axis of the second lens 2 is eliminated by mounting these on one and the same base plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module used for optical communication, and more particularly, to an optical module such as a semiconductor laser and a lens, which can be mounted without any alignment, thereby suppressing a decrease in optical output. The present invention relates to a structure of an optical module capable of improving productivity.

[0002]

2. Description of the Related Art As a conventional example of an optical module using two lenses, as disclosed in Japanese Patent Application Laid-Open No. 11-344463, a first lens is provided near a semiconductor laser and a second lens is provided. Are fixed to the package of the optical module. Light emitted from the semiconductor laser is converted into collimated light by the first lens, then collected by the second lens, and optically coupled to an optical fiber bonded to the package. Then, an optical isolator is arranged between the first lens and the second lens in order to reduce light returning to the semiconductor laser. According to this conventional technique, when a component on which a semiconductor laser and a first lens are mounted is fixed to a package, the optical axis is about several tens of microns between the first lens and a second lens fixed in advance to the package. The first lens and the second lens
Since the collimated light having a large light beam diameter passes between the lenses, the loss of optical coupling is small and the optical output can be stably extracted from the optical fiber.

[0003]

In the above conventional example, even if the optical axis between the first lens and the second lens fixed in advance to the package is shifted by about several tens of microns, the loss of optical coupling is small. It is slight. However, if the optical axis deviates by about several hundred microns, the loss becomes as large as tens of dB, and it becomes difficult to extract a high optical output from the optical fiber. In order to extract a high optical output from the optical fiber while minimizing the loss, the optical axis between the first lens and the second lens fixed in advance to the package is adjusted with some accuracy. There is a need. Specifically, a component on which the semiconductor laser and the first lens are mounted is arranged inside the package, and a line extending the optical axis between the semiconductor laser and the first lens is fixed on the second package. It was necessary to pass through the center of the lens. In addition, since the direction of this optical axis shift is the horizontal direction perpendicular to the optical axis and the height direction, when aligning the optical axis, observe these optical components from the top and observe the horizontal direction with respect to the optical axis. In addition to the alignment, the light in the height direction is considered in consideration of the variation in the thickness of the bonding agent for fixing the component on which the semiconductor laser and the first lens are mounted to the package and the variation in the height of the second lens fixed to the package. The axes had to be aligned. Therefore, there is a problem that it is difficult to obtain the throughput of the production quantity. In particular, in specifications that require high optical output, such as optical modules for long-distance transmission, a small shift in the optical axis causes a reduction in optical output, and it is difficult to maintain a stable yield in characteristics. was there.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and it is not necessary to align an optical axis between a semiconductor laser, a component including a first lens, and a second lens. Accordingly, an object of the present invention is to provide an optical module capable of improving productivity.

[0005]

According to the present invention, in order to achieve the above object, a semiconductor laser, a first lens, and a second lens are mounted on the same substrate. The semiconductor laser can be mounted with high accuracy by forming markers for alignment at predetermined positions on the semiconductor laser and the substrate, respectively, and comparing and aligning the markers with each other. . The first lens and the second lens are provided with mounting grooves at predetermined positions on the substrate, and are mounted on the respective portions. The mounting groove is such that when the first lens and the second lens are mounted on these portions, the emitted light from the semiconductor laser becomes almost collimated light via the first lens, and the beam of the collimated light The center is set so as to substantially match the center of the second lens. This eliminates the need for optical axis alignment between the first lens and the second lens, which was conventionally required with high accuracy.

Then, a light beam emitted from the semiconductor laser and passed through the first lens and the second lens is emitted from a substrate on which the semiconductor laser, the first lens, and the second lens are mounted. It is installed and fixed inside the package so as to pass through the exit window. In this case, even if the light emitted from the semiconductor laser and passing through the first lens and the second lens deviates from the center of the beam emission window by about 1 mm, the light from the second lens is coupled with minimal loss. The optical fiber can be positioned and fixed to the package as described above. Therefore, the substrate on which the semiconductor laser, the first lens, and the second lens are mounted can be fixed to the package without substantial alignment. As described above, an optical module with high productivity can be realized.

The grooves for mounting the first lens and the second lens formed on the substrate only need to be formed so that the optical axes are aligned, and any method can be used. When the grooves are formed with high positional accuracy, a method of forming the grooves in a V-groove shape with high accuracy by anisotropic etching using a semiconductor material such as Si or InP as a substrate can be used. Thereby, high positional accuracy of several microns or less can be realized. In the present invention, a method of forming the lens mounting groove other than the above-described anisotropic etching is not excluded, and any method including machining can be used as long as sufficient accuracy can be obtained.

Light emitted from the semiconductor laser and passed through the first lens and the second lens is guided to the optical fiber through the beam exit window of the package so that good optical coupling can be obtained. The set distance between the second lens and the optical fiber depends on the working distance of the second lens. Since the thickness of the package of about 1 mm is inserted between the second lens and the optical fiber, a margin of about 1.5 mm or more is expected in the distance between the second lens and the optical fiber. There is a need. When a spherical lens is used as the second lens, since the spherical lens has a small focal length, the size of the spherical lens is determined so as to obtain a required working distance. Specifically, when the refractive index of the spherical lens is 1.50, the diameter of the spherical lens needs to be 5 mm or more in order to secure the working distance of 1.5 mm or more. On the other hand, when an aspheric lens or a focusing rod lens is used as the second lens,
1.5m working distance even when the size is about 1-3mm
m or more. In this case, the size of the optical module can be further reduced.

If the first lens and the second lens can be configured to have substantially the same outer dimensions, the lens mounting grooves can be formed at the same depth. When the grooves are formed at the same depth, the two grooves can be formed at the same time regardless of whether they are formed by machining or anisotropic etching. There is an advantage.

When a stopper structure is provided in at least one of the groove for fixing the second lens, which is closer or farther from the first lens, the direction of the optical axis in fixing the second lens can be improved. Positioning is facilitated, and productivity is further improved.

The optical isolator is used to reduce the light returning to the semiconductor laser and to stably operate the semiconductor laser, and its size in the optical axis direction is usually about 2 mm. Depending on the type of semiconductor laser, it is necessary to provide an optical isolator. In this case, it is preferable to provide an optical isolator between the first lens and the second lens. On the other hand, the space between the first lens and the second lens is a portion through which the collimated light, which is substantially parallel light, passes.
An interval of about 2 to 4 mm can be secured. By installing the optical isolator in this portion, it is not necessary to increase the working distance and the size of the second lens more than necessary, so that the size of the package can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the drawings by using some embodiments.

FIG. 1 is a partially sectional side view showing a first embodiment of the optical module according to the present invention. In the figure, two lenses are shown, the first lens being a first spherical lens 1 and the second lens being a second spherical lens 2.
A V-groove 3 and a V-groove 4 are formed on a Si (silicon) substrate 5, and the first spherical lens 1 is positioned by the V-groove 3 so that
The second spherical lens 1 is mounted on the i-substrate 5, the second spherical lens 1 is positioned by the V groove 4, and mounted on the Si substrate 5, and further, the semiconductor laser 6 is mounted on the Si substrate 5. A component on which the semiconductor laser 6 and the first spherical lens 1 and the second spherical lens 2 are mounted is mounted on a metal stem 7. In this embodiment, the focal length of the second spherical lens 2 and V are adjusted so that the light emitted from the second spherical lens 2 passes through the beam exit window 12 and is focused in the optical fiber holder 15. Determine the position of the groove 4. The distance between the first spherical lens 1 and the semiconductor laser 6 is such that the light emitted from the semiconductor laser 6 is
After passing through the first lens, the position of the first spherical lens 1 is also determined by the V-groove 3 because it is determined that the light becomes parallel light.

In the example of FIG. 1, the V-groove 3 and the V-groove 4 are
It is formed by anisotropically etching the Si substrate 5, and the surface 5 of the Si substrate is made of SiO 2 by thermal oxidation.
An Si substrate on which a film is formed is used. The method of forming these grooves is not limited to the anisotropic etching method, and any method such as machining, processing by dry etching using plasma can be used, and the processing shape is also V-shaped. It is not limited. When the first spherical lens 1 and the second spherical lens 2 having substantially the same dimension in the height direction are used, the groove 3 and the groove 4 may have substantially the same depth. There is an advantage that the processing can be performed at the same time when these grooves are processed in the groove 5.

Next, the pedestal 8 is held on the metal stem 7, and the light receiving element 9 is mounted on the pedestal 8. Next, the metal stem 7 on which these components are mounted is fixed to the package 10. At this time, the metal stem 7 is placed at a predetermined position of the package 10 so that the optical axis of the light beam 11 passes through the center of the beam exit window 12 provided in the package 10.
Install and fix. That is, when the metal stem 7 is fixed to the package by soldering, the thickness of the metal stem 7 or the thickness of the metal stem 7 and the substrate 5 is designed in consideration of the thickness of the solder, and the horizontal direction (in the figure, Direction perpendicular to)
By performing the alignment described above, the light emitted from the second spherical lens 2 can pass through substantially the center of the beam emission window 12. When a Peltier element for radiating heat from the semiconductor laser 6 is provided between the metal stem 7 and the bottom surface of the package 10, the thickness of the metal stem 7 is designed in consideration of the thickness. .

Next, the package 10 is sealed by installing the lid 13 on the package 10. Next, the semiconductor laser 6
Is driven to emit a light beam 11, the optical fiber 14 and the optical fiber holder 15 are aligned so that the optical power extracted from the optical fiber 14 is maximized, and the optical fiber 14 and the optical fiber The holder 15 is fixed. Thus, the optical module is completed.

As described above, in this embodiment, the optical axis of the component composed of the semiconductor laser 6 and the first spherical lens 1 and the optical axis of the second spherical lens are aligned with the grooves 3 formed in the Si substrate 5. Since the alignment is automatically performed by the groove 4, it is not necessary to mechanically perform the precise axis alignment using a technique such as image processing separately, so that productivity can be improved. In this embodiment, the first and second spherical lenses 1 are used as lenses.
2 was used, but the lens was not limited to a spherical lens,
For example, a rod lens, an aspheric lens, or the like can be used.

FIG. 2 is a partially sectional side view showing a second embodiment of the optical module according to the present invention. In the illustrated embodiment,
An example in which an aspheric lens 2a is used instead of the second spherical lens 2 will be described. When the aspheric lens 2a is used, a groove is formed by shaving the substrate 5 so that the optical axis of the aspheric lens 2a substantially coincides with the optical axis of the first spherical lens 1. A stopper 16 is provided at the end of the Si substrate 5 on the surface on which is mounted, to position the aspherical lens 2a.
In this case, considering the focal length of the aspheric lens 2a, the light emitted from the aspheric lens 2a is
The position of the stopper 16 is determined so as to focus on the predetermined position.

FIG. 3 is a partially sectional side view showing a third embodiment of the optical module according to the present invention. In the illustrated embodiment,
Instead of the second spherical lens 2, a converging rod lens 2b
Here is an example using. When the converging rod lens 2b is used, a stopper 16 is provided at the end of the Si substrate 5 on the surface on which the converging rod lens 2b is mounted to position the converging rod lens 2b. In this case, in consideration of the focal length of the focusing rod lens 2b, the position of the light emitted from the focusing rod lens 2b is determined by the stopper 16 so as to focus on a predetermined position of the optical fiber holder 15. Also in the embodiment shown in FIGS. 2 and 3, by providing the stopper 16 for determining the position of the lens, the lenses 2a and 2b can be easily positioned and fixed at desired positions. Therefore, high productivity can be realized in the example of these lenses as in the example of FIG.

FIG. 4 is a partially sectional side view showing a fourth embodiment of the optical module according to the present invention. In the embodiment of FIG. 4, an optical isolator 17 is further added to the first embodiment shown in FIG.
Is shown between the spherical lens 1 and the aspherical lens 2a. Thereby, the amount of light emitted from the semiconductor laser 6 returning to the semiconductor laser 6 can be reduced to stabilize the operation of the semiconductor laser 6, and at the same time, by disposing the optical isolator 17 between the two lenses, the optical module It is not necessary to increase the size more than necessary. Whether the optical isolator 17 is necessary depends on the type of the semiconductor laser 6. For example, in the case of a DFB laser, an optical isolator 17 is required, and this embodiment is suitable for using such a semiconductor laser.

FIG. 5 is a partially sectional side view showing a fifth embodiment of the optical module according to the present invention. FIG. 5 shows an example in which a groove 18 for mounting the optical isolator 17 is further provided in the example shown in FIG. 4, and the optical isolator is arranged here. The groove 18 allows the mounting position of the optical isolator 17 to be easily known, thereby facilitating the mounting. Further, by appropriately setting the depth of the groove 18, the light beam 11 can pass through a substantially central portion of the optical isolator 17.

Although FIGS. 4 and 5 show the case where the second lens is an aspherical lens 2a, in each embodiment, the second spherical lens 2a is used as the second lens. Alternatively, a focusing rod lens 2b can be used.

FIG. 6 is a partially sectional side view showing a sixth embodiment of the optical module according to the present invention. In this embodiment, a Peltier element 61 is interposed between the metal stem 7 of the optical module shown in FIG. 4 and the bottom surface of the package 10 to radiate heat from the semiconductor laser 6 and the like. This Peltier element 61 is soldered to the package 10,
The Peltier element 61 and the metal stem 7 are soldered. The Peltier element 61 is, for example, a ceramic substrate 61
A semiconductor 61c is provided between a and 61b, and radiates heat by the Peltier effect. When the Peltier element 61 is used, the height from the bottom surface of the package 10 to the metal stem 7 is increased as compared with the embodiment of FIG. 4, so that the same metal stem 7 or substrate 5 as in FIG. Needs to change the height of the beam exit window 12.

FIG. 7 is a partial sectional side view showing a seventh embodiment of the optical module according to the present invention. The illustrated embodiment is an embodiment in which the first spherical lens 1 is replaced with an aspherical lens 71 in the embodiment of FIG. In the present embodiment, a stopper 72 is provided instead of the V-shaped groove 3. Since the stopper 72 properly maintains the space between the semiconductor laser 6 and the aspherical lens 72, the light emitted from the semiconductor laser 6 and emitted from the aspherical lens 71 becomes substantially parallel light. This embodiment has the same effect as the embodiment of FIG.

As described above, according to the present invention, a semiconductor laser, a first lens for collimating light emitted from a semiconductor laser, and a second lens for optically coupling the collimated light to an optical fiber Is mounted on the same substrate, an optical module with high productivity can be provided.

[0026]

As described above, according to the present invention, an optical module with high productivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial sectional side view showing a first embodiment of an optical module according to the present invention.

FIG. 2 is a partial sectional side view showing a second embodiment of the optical module according to the present invention.

FIG. 3 is a partial cross-sectional side view showing a third embodiment of the optical module according to the present invention.

FIG. 4 is a partial cross-sectional side view showing a fourth embodiment of the optical module according to the present invention.

FIG. 5 is a partial sectional side view showing a fifth embodiment of the optical module according to the present invention.

FIG. 6 is a partially sectional side view showing a sixth embodiment of the optical module according to the present invention.

FIG. 7 is a partial sectional side view showing a seventh embodiment of the optical module according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st spherical lens, 2 ... 2nd spherical lens, 2a ... Aspherical lens, 2b ... Focusing rod lens, 3 ... Groove, 4 ...
Groove, 5: Si substrate, 6: Semiconductor laser, 7: Metal stem, 8: Pedestal, 9: Light receiving element, 10: Package, 11
... light beam, 12 ... beam emission window, 13 ... cover, 14 ... optical fiber, 15 ... optical fiber holder, 16 ... stopper, 17 ... optical isolator, 18 ... groove.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazutani Kawamoto 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Technology Research Laboratory F-term (reference) 2H037 AA01 BA03 CA14 CA15 CA16 CA21 DA05 DA12 DA13 DA18 DA38

Claims (8)

[Claims] A semiconductor laser, a first lens for collimating light emitted from the semiconductor laser, and a second lens for optically coupling the collimated light to an optical fiber are mounted on the same substrate. An optical module, comprising: 2. An optical module according to claim 1, wherein said first lens or said second lens is mounted in a groove formed by anisotropically etching a part of said substrate. module. 3. The optical module according to claim 1, wherein said first lens is any one of a spherical lens, an aspherical lens, and a focusing rod lens, and said second lens is a spherical lens, an aspherical lens. And an optical module, which is one of a converging rod lens. 4. The optical module according to claim 2, wherein the grooves for mounting the first lens and the second lens have substantially the same depth. 5. The optical module according to claim 2, wherein the groove for mounting one or both of the first lens and the second lens has one or both of the first lens and the second lens. An optical module, characterized in that the optical module is a stopper for determining the position by aligning in the optical axis direction. 6. The optical module according to claim 1, wherein an optical isolator is arranged between said first lens and said second lens. 7. An optical module according to claim 6, wherein a groove for installing an optical isolator is provided on said substrate,
An optical module having an optical isolator installed at this position. 8. The optical module according to claim 1, wherein a package is provided, and a Peltier element is arranged between a bottom surface of the package and the substrate.